Spark plug boot and terminal



May 14, 1957 R. c. WOOFTER 2,792,558

SPARK PLUG BOOT AND TERMINAL Filed Sept. 2, 1954 50 INVENTOR. H9 2 Robert 0. Waoffer His Horngy United States Patent C i 2,72,558 SP PLUG BOOT AND TERMINAL Robert C. Woofier, Cortland, Ohio, assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Application September 2, 1954, Serial No. 453,792 3 Claims. (Cl. 33926) This invention relates to a boot adapted for placement on the insulator element of a spark plug and an electrical conductor terminal connection positioned within the boot for connection of the conductor to the spark plug with the boot providing a protective cover to prevent dirt and moisture from collecting on the terminal connection between the spark plug and the electrical conductor.

it has been common practice to provide terminal connections for the conductor wires between the distributor and the spark plug for an internal combustion engine with an elbow shaped terminal connector that frictionally fits upon the connector terminal of the spark plug. Flexible rubber boots have been provided around terminal connections with the ends thereof engaging the insulator of the spark plug and the conductor to prevent dirt and moisture from gaining access to the terminal connection between the conductor and the spark plug. However, it has been extremely difiicult to insert an elbow shaped conductor terminal into any flexible boot with the result that much expense is encountered when endeavoring to make such an assembly.

It has been desirable to use the elbow shaped conductor terminal for connection to a spark plug to eliminate long radius bends of a conductor wire on leaving its connection with the spark plug. The assembly of a rubber boot on an elbow shaped conductor terminal has become a necessity on the modern automobile engine because of its more critical performance. This has resulted in time consuming assembly operations that are desired to be eliminated.

While a spark plug boot having a very thin Wall and extreme flexibility will permit assembly of a boot on an elbow shaped spark plug connector, yet the extreme flexibility and thin wall of the boot does not provide for adequate sealing on the electrical conductor and the insulator on the spark plug to perform adequately the job of preventing access of dirt and moisture to the terminal connection between the terminal conductor and the spark plug.

It is therefore an object of this invention to provide a spark plug boot having generally an elbow shape of sufilcient wall thickness and rigidity that satisfactory r'riction engagement is obtained between a spark plug and a conductor to prevent access of moisture and dirt to the terminal connection, and to provide a terminal insertable into such a spark plug boot axially of the chamher that receives the conductor terminal and yet disposes the terminal end in a position receiving the spark plug terminal when the spark plug is received in the other end of the elbow shaped boot axially of the chamber that fits over the insulator of the spark plug.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings where in a preferred form of the invention is clearly shown.

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In the drawings:

Figure 1 is a diagrammatic elevational view of a V type internal combustion engine illustrating the use of the spark plug boot and terminal connection of this invention.

Figure 2 is a cross sectional view through the spark plug boot and terminal connection illustrating the conductor terminal in position on the spark plug terminal.

Figure 3 is a cross sectional view of the spark plug boot.

Figure 4 is a plan view of the conductor terminal.

Figure 5 is a view taken along line 5-5 of Figure 4.

Figure 6 is a plan view of a sheet metal blank from which the terminal is formed.

Figure 7 is a perspective view of the conductor terminal before placement on a conductor.

Figure 8 is a cross sectional view illustrating a conductor terminal and protective boot of the prior art.

In Figure 1 there is illustrated diagrammatically a V type internal combustion engine comprising the cylinder banks 19 and 11 and a crankcase 12. A conventional distributor 13 is mounted on the engine tor supplying electrical impulses to the spark plugs 14 and 15 providing for each of the cylinders of the cylinder banks It} and 11.

The spark plug 14 is connected with the distributor 13 by means of an electrical conductor 16. Similarly spark plug 15 is connected with the distributor 13 by means of an electrical conductor 17. The terminal connection between the conductor 16 and the spark plug 14 as well as between the conductor 17 and the spark plug 15 is covered by the protective boots 18 and 19 respectively. These protective boots are made of a resilient material that will frictionally engage the spark plug and the conductor inserted in opposite ends of the boot to hold tightly upon the same and prevent access of dirt and moisture to the terminal connection between the conductor and the spark plug.

In Figure 8 there is shown a. prior art practice of connecting the spark plug 20 with an electrical conductor 21 by means of an elbow shaped conductor terminal 22 that frictionally engages the spark plug terminal 23. A rubber boot 24 of generally elbow shape has one end receiving the spark plug 20 and the opposite end receiving the conductor 21 and the terminal 22.

However, the insertion of the elbow shaped terminal 22 through the passage 25 in the boot 24 is a diflicult procedure and has required time consuming operations out of proportion to the value obtained.

in this invention a conductor terminal that is illustrated in Figures 4 and 5 is provided for insertion into the protective boot illustrated in Figure 3 in a manner that the terminal is inserted into the boot on the axis of the chamber that receives it, and the terminal is formed so that the several portions thereof are all of substantially the same peripheral extent so that a straight axial movement of the terminal will place it in the boot without undue efiort and manipulation.

in Figure 6 there is illustrated the sheet metal blank from which the terminal of Figure 7 is made. The sheet metal blank comprises a fiat sheet metal part having a T-shaped portion 3%} comprising the head 31 and the stem 32. A fiat portion 33 extends from the bottom end of the stem 32 in the same plane thereof and angular to the longitudinal center line of the stem 32. A tang 34 may be struck up from the head portion 31 concurrently with the die forming of the blank.

The head portion 31 of the blank illustrated in Figure 6 is thereafter formed into a substantially U-shaped portion 35, as illustrated in Figure 7 and the extension 33 is formed into a substantially cylindrical portion 35 with the stem portion 32 of the blank interconnecting the portions 35 and 36 tangential to the respective portions.

The finished terminal 40 illustrated in Figure 7 is then placed upon a conductor wire 41 as illustrated in Figures 4 and 5, the conductor wire 41 being received within the U-shaped portion 35 of the terminal 49 and the upper ends of the U-shaped portion are closed upon the conductor 41 to'cncircle the same and retain the terminal 49 upon the end of the conductor 41. The tang 34 that has been struck up in the blanking operation pierces the insulation 41a of the conductor and engages the wire 4-2. Thus when the terminal 40 is placed upon the conductor 41 the head portion 31 of the terminal encircles the conductor substantially as a cylindrical portion with the stem portion 32 of the terminal being tangentiai to the thus formed circular head portion 31 and is tangential to the circular portion 36 as illustrated in Figure 5.

As shown in Figures 4 and the transverse extremities of the terminal portion 36 is substantially within an area defined by the outer periphery of the circular portion of the terminal encircling the conductor 41 as projected forwardly along the axis of the terminal portion 35. Also, the axis of the circular portion 36 is parallel to aplane that is parallel to both the axes of the circular portion 31 and the circular portion as it encircles the conductor intact the axis of the circular portion 36 is in substantially a common plane with the axis of the circular portion 35 as illustrated in the drawings. Further, the axis of the circular portion 36 is also angular to the axis of the circular portion 35 so that when the circular portion 36 is disposed Within the boot illustrated in Figure 3 the circular portion 36 will be coaxial with the chamber of the boot adapted. to receive the terminal end of the spark plug.

The spark plug boot is illustrated in Figure 3 and has the general form of an elbow and is preferably made of a semi-rigid rubber-like material that has some degree of flexibility that it will securely frictioually bind upon the conductor and the spark plug received into the boot. The spark plug boot 50 has the part 51 provided with an axially extending chamber 52 and the part 53 provided with the axially extending chamber 54, both of which chambers 52 and 54 interconnect at their juncture 55. The chamber 52 is adapted to receive the insulator element of a spark plug while the chamber 54 is adapted to receive the terminal illustrated in. Figure 4. In fact the terminal illustrated in Fig. 4 is inserted axially into the chamber 54 of the boot 50 in a direct axial movement, just as though the terminal in Fig. 4 has been moved directly into the chamber 54 of the boot 53 of Fig. 3 so that the terminal will be positioned in the boot as shown in Figure 2. Since all portions of the terminal 49 are substantially within the same laterally extending area, the terminal can be inserted into the boot by a direct axial thrust into the chamber 54.

When the terminal 4-0 is inserted into the boot 50 as shown in Figure 2, the portion 36 of the terminal 40 has its axis coaxial with the axis of the chamber 52 of the boot 58. Thus the insulator end of the spark plug 15 is received by direct axial thrust into the chamber 52 with the spark plug terminal 61 being thrust axially into the cylindrical portion 36 of the terminal 40.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted as may come within the scope of the claims which follow.

What is claimed is as follows:

1. For use with a spark plug adapted to be secured in the cylinder block of an engine, the spark plug having an insulator element and a connector terminal supported thereby adapted to be engaged by a terminal on one end of an electrical conductor for connection of the conductor to the spark plug, connector terminal with the conductor extending from the spark plug angularly relative to the axis of the spark plug, the combination of, a protective boot adapted to prevent access of dirt and moisture to the connector terminal and conductor connection comprising a casing of a semi-rigid insulating material having some resiliency, said casing having a first part provided with an axially extending chamber therein adapted to receive the insulator element and provide a tight fit thereon and a second part disposed angularly to the first part and provided with an axially extending chamber connected with the chamber in the first part to receive an electrical conductor terminal and conductor portion and provide a tight fit on the conductor portion, and an electrical conductor having a terminal on one end disposed in the said chamber in said second part with the terminal end disposed at the juncture of the said chambers, said conductor terminal comprising a first portion on the longitudinal axis of the conductor encircling the conductor and attaching the terminal to said conductor and positioned coaxially in said chamber in said secand part and including an annular plug terminal engaging second portion adapted to receive the plug terminal with the axis of said second portion angular to the axis of the first portion and coaxial with the axis of the first chamher and parallel to a connecting plane portion tangent to and contiguous with both terminal portions that are at opposite ends of said plane portion wit said plane portion being positioned parallel to both said axes and extending longitudinally from one end of said first portion in the direction of the axis of saidfirst terminal portion.

2. A structure in accordance with claim 1 in which the second portion of said conductor terminal is an annulus disposed axially. forward of the first portion of the conductor terminal which is an annulus and has the peripheral extremities thereof disposed substantially within an area defined by the periphery of the first portion as extended axially forward of the first portion.

3. A structure in accordance with claim 1 in which the second portion of said conductor terminal is an annulus disposed axially forward of the first portion of the conductor terminal which is an annulus and has the peripheral extremities thereof disposed substantially within an area defined by the periphery of said first portion as extended axially forward of the first portion, with the said second portion of said conductor terminal on the same side of said connecting plane portion as said first portion thereof.

References Cited in the file of this patent UNITED STATES PATENTS 2,374,413 Carlson Apr. 24, 1945 2,439,947 Pontius Apr. 20, 1948 2,451,809 Buchanan Oct. 19, 1948 2,665,673 Woofter Jan. 12, 1954 2,690,541 Elliott Sept. 28, 1954 FOREIGN PATENTS 505,312 Canada Aug. 24, 1954 

